GPU Cmake: allow unsupported GCC only if we don't autodetect CUDA

Author: davidrohr

dependencies/FindO2GPU.cmake

@@ -111,10 +111,13 @@ if(ENABLE_CUDA)
     endif()
   endif()
   if(CMAKE_CUDA_COMPILER)
-    set(CMAKE_CUDA_FLAGS "-Xcompiler \"${O2_GPU_CMAKE_CXX_FLAGS_NOSTD}\" ${CMAKE_CUDA_FLAGS} --expt-relaxed-constexpr --extended-lambda --allow-unsupported-compiler -Xptxas -v -Xcompiler -Wno-attributes")
+    set(CMAKE_CUDA_FLAGS "-Xcompiler \"${O2_GPU_CMAKE_CXX_FLAGS_NOSTD}\" ${CMAKE_CUDA_FLAGS} --expt-relaxed-constexpr --extended-lambda -Xptxas -v -Xcompiler -Wno-attributes")
     if(CMAKE_CUDA_COMPILER_VERSION VERSION_GREATER_EQUAL "12.3")
       string(APPEND CMAKE_CUDA_FLAGS " -Xcudafe --diag_suppress=20257") # TODO: Cleanup
     endif()
+    if (NOT ENABLE_CUDA STREQUAL "AUTO")
+      string(APPEND CMAKE_CUDA_FLAGS " --allow-unsupported-compiler")
+    endif()
     set(CMAKE_CUDA_FLAGS_${CMAKE_BUILD_TYPE_UPPER} "-Xcompiler \"${CMAKE_CXX_FLAGS_${CMAKE_BUILD_TYPE_UPPER}}\" ${CMAKE_CUDA_FLAGS_${CMAKE_BUILD_TYPE_UPPER}}")
     if(CMAKE_BUILD_TYPE_UPPER STREQUAL "DEBUG")
       set(CMAKE_CUDA_FLAGS_${CMAKE_BUILD_TYPE_UPPER} "${CMAKE_CUDA_FLAGS_${CMAKE_BUILD_TYPE_UPPER}} -lineinfo -Xptxas -O0 -Xcompiler -O0")